Temperature controlled variable reflectivity coatings

ABSTRACT

Coatings configured to change between a relatively higher reflectivity state and a relatively lower reflectivity state depending at least partially upon temperature are generally disclosed. Some example coatings may include a selectively reflective layer including a plurality of microcapsules, which may include an ionic liquid and/or a surfactant within a shell. The microcapsules may have a relatively higher reflectively when at temperatures above a cloud transition temperature and/or a relatively lower reflectivity when at temperatures below the cloud transition temperature. When at temperatures above the cloud transition temperature, the selectively reflective layer may reflect a first fraction of the incident light. When at temperatures below the cloud transition temperature, the selectively reflective layer may reflect a second fraction of the incident light. The first fraction of the incident light may be greater than the second fraction of the incident light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry of PCT/US2011/026610, filedMar. 1, 2011, which is hereby incorporated by reference.

BACKGROUND

The present disclosure generally pertains to coatings and, moreparticularly, to coatings that may vary in reflectivity based at leastin part upon temperature.

SUMMARY

Coatings are generally disclosed. Some example embodiments may includemethods, apparatus, and/or systems pertaining to coatings that may beconfigured to change their ability to transmit and/or reflect light inresponse to changes in temperature. For example, some embodimentsaccording to the present disclosure may pertain to coatings forsurfaces, such as surfaces of structures, that may vary in reflectivitybased at least in part upon temperature.

Some example coatings for substrates according to the present disclosuremay be configured to change between a relatively higher reflectivitystate and a relatively lower reflectivity state depending at leastpartially upon a temperature of at least a portion of the coating. Someexample coatings may include a selectively reflective layer including aplurality of microcapsules. Individual microcapsules may include anionic liquid and/or a surfactant within a shell. The microcapsules mayhave a relatively higher reflectively when at temperatures above a cloudtransition temperature and/or a relatively lower reflectivity when attemperatures below the cloud transition temperature. When attemperatures above the cloud transition temperature, the selectivelyreflective layer may reflect a first fraction of incident light. When attemperatures below the cloud transition temperature, the selectivelyreflective layer may reflect a second fraction of the incident light.The first fraction of the incident light may be greater than the secondfraction of the incident light.

Some example methods according to the present disclosure may pertain toapplying a coating configured to change between a relatively higherreflectivity state and a relatively lower reflectivity state dependingat least partially upon a temperature of at least a portion of thecoating. Some example methods may include applying a selectivelyreflective layer on a generally light-absorbent base layer. Theselectively reflective layer may include a plurality of microcapsulesdisposed between a source of incident light and the generallylight-absorbent base layer. Individual microcapsules may include anionic liquid and a surfactant within a shell. The microcapsules may havea relatively higher reflectively when at temperatures above a cloudtransition temperature and a relatively lower reflectivity when attemperatures below the cloud transition temperature. When attemperatures above the cloud transition temperature, the selectivelyreflective layer may reflect a first fraction of the incident light.When at temperatures below the cloud transition temperature, theselectively reflective layer may reflect a second fraction of theincident light. The first fraction of the incident light may be greaterthan the second fraction of the incident light.

Some example selectively reflective construction materials according tothe present disclosure may be configured to change between a relativelyhigher reflectivity state and a relatively lower reflectivity statedepending at least partially upon a temperature of at least a portion ofthe material. Some example materials may include a base layer includinga generally light-absorbent surface. A selectively reflective layerincluding a plurality of microcapsules may be disposed on the generallylight-absorbent surface between a source of incident light and thegenerally light-absorbent surface. Individual microcapsules may have arelatively higher reflectively when at temperatures above a transitiontemperature and a relatively lower reflectivity when at temperaturesbelow the transition temperature. When at temperatures above thetransition temperature, the selectively reflective layer may reflect afirst fraction of the incident light. When at temperatures below thetransition temperature, the selectively reflective layer may reflect asecond fraction of the incident light, the first fraction of theincident light being greater than the second fraction of the incidentlight.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

In the drawings:

FIG. 1 is a cross-sectional view of an example temperature-controlledcoating below and above a cloud transition temperature;

FIG. 2 is a cross-sectional view of an example temperature-controlledcoating below a cloud transition temperature;

FIG. 3 is a cross-sectional view of an example temperature-controlledcoating above a cloud transition temperature;

FIG. 4 is an elevation view of a structure including exampletemperature-controlled coatings; and

FIG. 5 is a flow chart illustrating an example method of applying acoating; all arranged in accordance with at least some embodiments ofthe present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, may be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

Methods, systems, devices, and/or apparatus pertaining to coatings thatmay be configured to change their ability to transmit and/or reflectlight in response to changes in temperature are generally described.Some example embodiments according to the present disclosure may pertainto coatings for surfaces, such as surfaces of structures, that may varyin reflectivity based at least in part upon temperature.

Some example coatings according to the present disclosure may beconfigured to change between a relatively higher reflectivity state anda relatively lower reflectivity state depending at least partially upona temperature of at least a portion of the coating. Some examplecoatings may include a selectively reflective layer including aplurality of microcapsules that may have a relatively higherreflectively when at temperatures above a particular temperature and/ora relatively lower reflectivity when at temperatures below theparticular temperature.

Some example coatings according to the present disclosure may be used onstructures, such as buildings. For example, some coatings according tothe present disclosure may be used as an exterior coating for abuilding. Some example coatings may react to the outside temperature tobecome less light-reflective on cold days and/or more light-reflectiveon warm days. At cooler temperatures, at least some incident light maypass through the coating and may produce a solar heating effect on thebuilding. At warmer temperatures, the coating may reflect more light,thereby reducing the amount of light passing through the coating, whichmay allow relatively less solar heating. Thus, some example coatings maybe used to reduce heating and/or cooling costs for the building.

As used herein, “reflectivity” may refer to the fraction of incidentlight that is reflected by a surface. In some example embodimentsaccording to the present disclosure, a change in temperature of at leasta portion of a coating may produce a change in the reflectivity of thecoating.

FIG. 1 is a cross-sectional view of an example temperature-controlledcoating 100 below and above a cloud transition temperature, inaccordance with at least some embodiments of the present disclosure.Coating 100 may comprise a selectively reflective layer 122, which maycomprise a plurality of microcapsules 102, 104, 106, 108, 110, 112, 114,116. Microcapsules 102, 104, 106, 108, 110, 112, 114, 116 may be adheredto each other and/or to a base layer 118 by a binder 120, which may besubstantially transparent.

In some example embodiments according to the present disclosure, baselayer 118 may include a generally light-absorbent surface 124 and/or maybe disposed on a substrate 126. In some example embodiments, substrate126 may be generally thermally conductive. In some example embodiments,base layer 118 may be generally dark in color. Base layer 118 maycomprise paint, which may be brushed, sprayed, and/or rolled ontosubstrate 126. Similarly, in some example embodiments, selectivelyreflective layer 122 may be brushed, sprayed, and/or rolled onto baselayer 118.

Microcapsules 102, 104, 106, 108, 110, 112, 114, 116 are described withspecific reference to microcapsule 114; however, it is to be understoodthat other microcapsules 102, 104, 106, 108, 110, 112, 116 (and someother microcapsules according to the present disclosure) may besubstantially similar to microcapsule 114. Microcapsule 114 may includean outer shell 114S, which may substantially surround a core 114C. Someexample shells 114S may be formed from substantially transparent and/orsubstantially translucent materials, such as polysulfone and/or otherthermoplastic polymers.

In some example embodiments according to the present disclosure,microcapsule 114 may have a size of about 100 μm to about 2 mm. In someexample embodiments, microcapsule 114 may have a size of about 100 μm toabout 200 μm.

In some example embodiments according to the present disclosure, core114C may have temperature-sensitive properties. For example, in someexample embodiments, core 114C may comprise an ionic liquid (IL) and/ora surfactant (e.g., a glycol ether). Below a cloud transitiontemperature (T_(C)), the ionic liquid and/or the surfactant maycomprises a solution that is substantially transparent. As thetemperature increases above T_(C), the surfactant may separate out ofthe ionic liquid, such as because of a conformational change in theglycol polymer. The surfactant may form micelles 114M in the ionicliquid. Miscelles 114M may have sufficiently large hydrodynamicdiameters to scatter light, which may give core 114C a generally cloudyappearance. This phenomenon may be referred to as the “cloud point.”

When the temperature of core 114C falls below T_(C), miscelles 114M maydissipate, which may return core 114C to a substantially transparentstate. The left portion of FIG. 1 illustrates coating 100 at atemperature below T_(C) (e.g., T<T_(C)), while the right portion of FIG.1 illustrates coating 100 at a temperature above T_(C) (e.g., T>T_(C)).In some example embodiments, core 114C in the generally transparentstate may reflect substantially less light than when core 114C isgenerally cloudy. Thus, microcapsule 114 may change between a relativelyhigher reflectivity state and a relatively lower reflectivity statedepending at least partially upon its temperature.

Generally, shell 114S, the ionic liquid, and/or the surfactant may beselected to be substantially non-volatile, substantially light-stable,and/or substantially oxygen-stable. Example ionic liquids include, butare not limited to, 1-butyl-3-methytimidazoliumbis(trifluoromethysulfonyl)amide, BmimBF4, EmimBF4, HmimBF4, EMI-OTf,EMI-Im, HMI-OTf, HMI-Im, and/or BMP-OTf. Example surfactants include,but are not limited to, poly(oxyethylene) alkyl etherH(CH₂)₁₄(OCH₂CH₂)₆OH, C₁₄E₆, C₁₄E₅, C₁₂E₆, and/or C₁₂E₅.

In some example embodiments, core 114C may comprise a surfactant thatmay be neither highly soluble nor insoluble in the ionic liquid. Thismay be achieved, for example, by using an ionic liquid such as BmimBF4and/or a mixed alkyl/PEO surfactant such as C14E6.

In some example embodiments, the surfactant and ionic liquid may beprovided in quantities of about 5% to about 95% ionic liquid and/orabout 5% to about 95% surfactant. For a particular surfactant and aparticular ionic liquid, T_(C) may vary as the relative proportions ofthe surfactant and/or ionic liquid are varied. Thus, a desired T_(C) maybe achieved by adjusting the relative proportions of the surfactantand/or ionic liquid comprising core 114C.

In some example embodiments, core 114C may include a mixture containingtwo or more ionic liquids. For example, core 114C may include an ionicliquid mixture comprising about 50% EmimBF4 and/or about 50% HmimBF4. Insuch an example embodiment, EmimBF4 may be a relatively less effectivesolvent for the surfactant and/or HmimBF4 may be a relatively moreeffective solvent for the surfactant. Such mixtures of ionic liquids mayprovide the desired solvent characteristics, which may be useful foradjusting T_(C) as desired.

In some example embodiments, core 114C may be configured such that T_(C)is between about 10 degrees C. and about 50 degrees C. In a detailedexample embodiment, T_(C) may be between about 25 degrees C. and about35 degrees C. Specific examples of T_(C) include about 25 degrees C.,about 27 degrees C., about 29 degrees C., about 31 degrees C., about 33degrees C., about 35 degrees C., and temperatures between any two ofthese values. In a detailed example embodiment according to the presentdisclosure, T_(C) may be about 30 degrees C.

FIG. 2 is a cross-sectional view of an example temperature-controlledcoating 200 below a cloud transition temperature, in accordance with atleast some embodiments of the present disclosure. Coating 200 may begenerally similar to coating 100 described above. Coating 200 maycomprise a selectively reflective layer 201, which may comprise aplurality of microcapsules 202, 204, 206, 208, 210, 212, 214, 216, 218,220, 222, 224. Selectively reflective layer 201 may be disposed betweena source 234 of incident light 232 and a base layer 226, which may beprovided on a substrate 228. For example, selectively reflective layer201 may be disposed on base layer 226.

Coating 200 may have a thickness 230. In some example embodimentsaccording to the present disclosure, thickness 230 may be about 100 μmto about 5 mm. In some example embodiments, thickness 230 may be about200 μm to about 2 mm.

Incident light 232 from source 234 (e.g., the sun) may strike coating200. Coating 200 may reflect a fraction 236 of incident light 232 and/ormay transmit at least a portion 238 of incident light 232 to base layer226. Because the temperature of coating 200 is less than about T_(C),individual microcapsules 202, 204, 206, 208, 210, 212, 214, 216,2 18,220, 222, 224 may be substantially transparent, which may give coating200 a substantially transparent appearance. In some example embodiments,when the temperature of coating 200 is less than about T_(C), fraction236 of incident light 232 that is reflected by selectively reflectivelayer 201 may be less than about 50%. In some example embodiments, whenthe temperature of coating 200 is less than about T_(C), fraction 236 ofincident light 232 that is reflected by selectively reflective layer 201may be less than about 20%.

FIG. 3 is a cross-sectional view of example temperature-controlledcoating 200 above a cloud transition temperature, in accordance with atleast some embodiments of the present disclosure. Because thetemperature of coating 200 is above about T_(C), individualmicrocapsules 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224may be substantially cloudy due to the presence of micelles 240. In someexample embodiments, when the temperature of coating 200 is above aboutT_(C), fraction 236 of incident light 232 that is reflected byselectively reflective layer 201 may be at least about 50%. In someexample embodiments, when the temperature of coating 200 is above aboutT_(C), fraction 236 of incident light 232 that is reflected byselectively reflective layer 201 may be at least about 80%.

FIG. 4 is an elevation view of a structure 400 including exampletemperature-controlled coatings 402, 404, in accordance with at leastsome embodiments of the present disclosure. Some example coatings 402according to the present invention may be disposed on and/or comprise aroofing material 406 of structure 400. Some example coatings 404according to the present disclosure may be disposed on and/or maycomprise a part of a wall covering material 408 of structure 400.Roofing material 406, wall covering material 408, and/or other materialsused to construct structures may be referred to as constructionmaterials.

In some example embodiments according to the present disclosure, roofingmaterial 406 and/or wall covering material 408 may comprise a substrate(e.g., generally similar to substrate 126 and/or substrate 228). In someexample embodiments, roofing material 406 and/or wall covering material408 may be installed on structure 400 after coatings 402, 404 have beenat least partially applied to roofing material 406 and/or wall coveringmaterial 408. For example, roofing material 406 and/or wall coveringmaterial 408 may be installed on structure 400 after a generallylight-absorbent base layer has been applied to the substrate and/orafter a selectively reflective layer has been applied to the base layer.

In some example embodiments, roofing material 406 and/or wall coveringmaterial 408 may be installed on structure 400 before coatings 402, 404have been fully applied to roofing material 406 and/or wall coveringmaterial 408. For example, roofing material 406 and/or wall coveringmaterial 408 may be installed on structure 400 before a generallylight-absorbent base layer has been applied to the substrate and/orbefore a selectively reflective layer has been applied to the baselayer.

FIG. 5 is a flow chart illustrating an example method 500 of applying acoating, in accordance with at least some embodiments of the presentdisclosure. The coating may be configured to change between a relativelyhigher reflectivity state and a relatively lower reflectivity statedepending at least partially upon a temperature of at least a portion ofthe coating. Method 500 may include operation 502, which may includeapplying a selectively reflective layer on a generally light-absorbentbase layer, the selectively reflective layer comprising a plurality ofmicrocapsules disposed between a source of incident light and thegenerally light-absorbent base layer, individual microcapsulescomprising an ionic liquid and a surfactant within a shell, themicrocapsules having a relatively higher reflectively when attemperatures above a cloud transition temperature and a relatively lowerreflectivity when at temperatures below the cloud transitiontemperature. In some example embodiments, when at temperatures above thecloud transition temperature, the selectively reflective layer mayreflect a first fraction of the incident light. In some exampleembodiments, when at temperatures below the cloud transitiontemperature, the selectively reflective layer may reflect a secondfraction of the incident light. In some example embodiments, the firstfraction of the incident light may be greater than the second fractionof the incident light.

Some example coatings according to the present disclosure may allow somecharacteristics (e.g., color, texture, etc.) of a substrate to bevisible through the coating. Generally, the visible appearance of someexample coatings may be dependent primarily upon the underlying baselayer. In some example embodiments, the exact hue and/or pattern of thebuilding's surface may be selected by the building's architect whileretaining the selectively reflective features of the coating.

Some example coatings according to the present disclosure may be appliedto and/or may comprise parts of buildings besides wall coveringmaterials and/or roofing materials. For example, some example coatingsmay be applied to and/or may comprise windows, skylights, and/or othersimilar construction materials. Further, some example coatings accordingto the present disclosure may be applied to and/or may comprise parts ofvehicles (e.g., automobiles, boats, trains, etc.), such as wall coveringmaterials, roofing materials, and/or window materials for vehicles.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely examples, and that in fact many other architectures may beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated may also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated may also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art may translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A coated substrate comprising a substrate and acoating on the substrate, the coating being configured to change betweena relatively higher reflectivity state and a relatively lowerreflectivity state depending at least partially upon a temperature of atleast a portion of the coating, the coating comprising: a selectivelyreflective layer comprising a plurality of microcapsules, the pluralityof microcapsules comprising an ionic liquid and a surfactant within ashell, the plurality of microcapsules having a relatively higherreflectively when at temperatures above a cloud transition temperatureand a relatively lower reflectivity when at temperatures below the cloudtransition temperature; wherein, when at temperatures above the cloudtransition temperature, the selectively reflective layer reflects afirst fraction of incident light; and wherein, when at temperaturesbelow the cloud transition temperature, the selectively reflective layerreflects a second fraction of the incident light, the first fraction ofthe incident light being greater than the second fraction of theincident light.
 2. The coated substrate of claim 1, wherein theselectively reflective layer can be disposed between a source of theincident light and a light-absorbent surface of a base layer.
 3. Thecoated substrate of claim 2, wherein the selectively reflective layer isdisposed on the light-absorbent surface of the base layer.
 4. The coatedsubstrate of claim 2, wherein the light-absorbent surface of the baselayer is dark in color.
 5. The coated substrate of claim 1, wherein theselectively reflective layer includes a transparent binder.
 6. Thecoated substrate of claim 1, wherein the selectively reflective layer isabout 100 μm to about 5 mm in thickness.
 7. The coated substrate ofclaim 1, wherein the selectively reflective layer is about 200 μm toabout 2 mm in thickness.
 8. The coated substrate of claim 1, wherein theplurality of microcapsules are about 100 μn to about 2 mm in size. 9.The coated substrate of claim 1, wherein the plurality of microcapsulesare about 100 μm to about 200 μm in size.
 10. The coated substrate ofclaim 1, wherein, when at temperatures above the cloud transitiontemperature, the selectively reflective layer reflects at least about80% of the incident light.
 11. The coated substrate of claim 1, wherein,when at temperatures below the cloud transition temperature, theselectively reflective layer reflects less than about 20% of theincident light.